	// base64加密开始 --> 
	var keyStr = "ABCDEFGHIJKLMNOP" +"QRSTUVWXYZabcdef" +"ghijklmnopqrstuv" +"wxyz0123456789+/" + "="; 

	function encode64(input) { 

	var output = ""; 
	var chr1, chr2, chr3 = ""; 
	var enc1, enc2, enc3, enc4 = ""; 
	var i = 0; 
	do 
	{ 
	chr1 = input.charCodeAt(i++); 
	chr2 = input.charCodeAt(i++); 
	chr3 = input.charCodeAt(i++); 
	enc1 = chr1 >> 2; 
	enc2 = ((chr1 & 3) << 4) | (chr2 >> 4); 
	enc3 = ((chr2 & 15) << 2) | (chr3 >> 6); 
	enc4 = chr3 & 63; 
	if (isNaN(chr2)){ 
	enc3 = enc4 = 64; 
	}else if (isNaN(chr3)){ 
	enc4 = 64; 
	} 
	output = output + 
	keyStr.charAt(enc1) + 
	keyStr.charAt(enc2) + 
	keyStr.charAt(enc3) + 
	keyStr.charAt(enc4); 
	chr1 = chr2 = chr3 = ""; 
	enc1 = enc2 = enc3 = enc4 = ""; 
	} while (i < input.length); 

	return output; 
	   
	}	
	//- base64加密结束